1. Field of the Invention
The invention relates to an information recording medium, a recorder, a reader and a reading method. It can be applied notably to magnetic or optical media wherein the information elements are arranged in the form of parallel tracks. It relates more particularly to a track-following system.
The invention can be applied notably to computer peripheral recording and reading systems and to all systems of a professional type.
In particular, the invention provides solutions for track following and for the elimination of cross-talk in fixed-head reading systems.
2. Discussion of Background
Present-day systems have low track density (with a pitch of over 100 .mu.m). The tracks are separated by blank signal barriers to prevent reading cross-talk. This is ensured by heads that are less wide than the tracks. The checking of the position of the edge of the tape is enough to ensure efficient following of the track and interoperational quality of the tapes and readers for the tracks are wide.
Fixed-head systems cannot therefore hope to have high track density.
In digital information recording systems, each information element is constituted by positive (or zero) elements and negative elements. In the different tracks, the number of positive and negative elements is different. This gives rise to a non-zero continuous component.
To prevent this, a channel encoder that carries out a transcoding is used: a certain number of incoming bits will be encoded in the form of a higher number of magnetic domains, leaving sufficient freedom to eliminate the continuous component. Use will be made, for example, of the 8-10 code in which an 8-bit information element is encoded by means of 10 bits. This means that the 256 information elements possible with an 8-bit code use only 256 bits out of 1024 of a 10-bit code.
If values of +1 or -1 are assigned to the magnetic domains according to their direction, DSV designates the integral of these values on a track. Certain 10-bit recording codes therefore make it possible to limit the variations of the DSV around the zero value.
The invention modifies this encoding of information elements so as to enable a track-following system.